Knee osteoarthritis (OA) accounts for a significant proportion of mobility limitations and is one of the most disabling problems facing the growing population of older adults. The long-term objective of this research is to reduce disablement of older adults with symptomatic knee OA. The principle of specificity of training indicates that exercises that closely approximate the goal functional activity are most effective in improving physical performance during that activity. Based on this principle, the specific aims of this project are to design a patient-specific gait training intervention using analysis of compensatory joint moments and energy expenditure, and then to assess the effect of this gait training intervention and a mobility-specific power training program on improving mobility limitations, disability and quality of life in older adults with symptomatic knee OA. This will be accomplished through assessing the effects on pathology (muscle composition by single slice CT), impairments (muscle power), and functional limitations (standing and walking) with each intervention in a randomized controlled trial. The power training intervention is a weighted vest program, previously shown to improve functional mobility among community dwelling older adults. The next logical step is to extend this research to individuals with knee OA. Understanding the changes that occur in lower limb muscle with each of these interventions will guide future therapeutic interventions and characterize which subjects may need additional attention. Successful completion will inform rehabilitation for maintaining or improving mobility as well as explore the mechanism of effect. This project is proposed as part of a career development plan. The candidate's long-term career goal is to sustain an independent patient-oriented research program that will guide therapy for minimizing mobility limitations and disability in older adults with knee OA. The mentorship, didactic, and professional experiences proposed will provide training in assessment of muscle composition, strength and power, use of biomechanical motion analysis and physical performance testing, and skills in research methodologies and responsible conduct. The candidate is an Assistant Professor in the Department of Orthopaedics and Rehabilitation at the University of Iowa (Ul). This department, as well as the Ul College of Medicine, the Ul Center on Aging, and the General Clinical Research Center are strongly committed to supporting the candidate and research to benefit older adults. This substantial commitment will enhance training and research productivity, enabling the candidate to become an independent investigator who will advance physical function in older adults.